Unplug the pumps electrical connector, activate the central locking and check that the pump has a power and earth using a multimeter, if it does then its most likely the pump has gone wrong, but defintately check its getting 12v, not just using a test lamp.
If it doesn't have power or no connection to earth then start checking your fuses and wiring. I don't know off hand what fuse number it is but it will be on the reverse of the fuse box cover.
Do you have remote central locking or is it through the drivers door pin its activated?
